1. Field of the Invention
The present invention generally relates to methods of reading bar codes and bar-code reading devices, and particularly relates to a method of reading bar codes and a bar-code reading device which is equipped with a hand-held bar-code reader using a laser light.
In recent years, laser-based bar-code readers have been widely used as often seen in POS (point of sales) systems in a distribution industry, and such readers are generally fixed to a check-out counter while allowing bar codes to be read in a non-contacting manner. An ever increasing range of products requires diversified use of such bar-code readers. Efforts thus have been directed to development of a hand-held bar-code reader, which can be picked up from a fixed position on the counter where it is used as a fixed-type bar-code reader, in order to cope with a variety of products at the check-out counter.
2. Description of the Prior Art
Hand-held bar-code readers are often used for reading bar-code menus.
The bar-code menus are useful when bar-code labels cannot be attached to some types of products. When unlabeled products need to be processed, a bar-code reader is used for reading bar codes on a separate bar-code menu which gives a list of the unlabeled products. Bar-code readers for reading the bar-code menus typically include a pen-type bar-code reader and a touch-scanner-type bar-code reader, which have a relatively short (sensor) readable range. Because of the short readable range, these types of bar-code readers need to come in-contact with bar codes in order to read the bar codes.
On the other hand, laser-based bar-code readers are characterized by having a long (sensor) readable range. The long readable range allows the laser-based bar-code readers fixedly mounted on check-out counters to read bar codes when products with bar-code labels are shown, i.e., exposed or presented to a scan window of the readers. These bar-code readers can read bar codes as long as the bar codes are presented within a certain range from the scan window. Operators do not have to be overly sensitive about positions of products when showing the products with bar-code labels to the bar-code readers. This type of bar-code reader is suitable for reading a go large number of bar codes in a short period of time.
Recent development of technology has made it possible to create laser-based bar-code readers which are normally mounted to a counter, but can also be used as hand-held readers as such a need arises. These bar-code readers are mounted to a counter table or the like to read bar codes when products with bar-code labels are processed. When there is a need to read a separate bar-code menu with respect to unlabeled products or there is a need to read a bar code attached to a heavy product which cannot be held by hand over the scan window, the bar code reader is detached from the counter table to read the bar-code menu or the bar code on the heavy product.
The laser-based hand-held bar-code readers have a long readable range as do the fixedly mounted laser-based bar-code readers. When there is a need to read a separate bar-code menu, what is expected most of the time is to read only a couple of bar codes among many bar codes recorded on the bar-code menu. Since an intended bar code is listed among other bar codes, use of bar-code readers having a long readable range may result in reading other unnecessary bar codes along with the intended bar code. Further, even during a time when an operator brings a bar-code reader closer to the intended bar code, laser-scan light continues to be emitted from the scan window of the bar-code reader, ending up scanning irrelevant bar codes.
Some of the laser-based hand-held bar-code readers obviate this problem by making the sensor readable range shorter when the bar-code readers are used in a hand-held manner. With a shortened readable range, bar-code readers do not pick up unnecessary bar codes other than the intended bar code. When this configuration is used, however, the merit of the long readable range cannot be utilized to the full extent. Bar-code readers may be used for other purposes than reading a bar-code menu, as in the case of a heavy product, wherein it is preferable to have a long readable range to read a bar code from some distance. Such demand cannot be met if bar-code readers are limited to a short readable range when picked up by hand.
Further, even with a shortened readable range, bar-code readers may pick up unnecessary bar codes because the readers keep emitting laser-scan light from the scan window. Especially, when the bar-code readers are handled carelessly, there is an increased chance of reading irrelevant bar codes.
Accordingly, there is a need for a method of reading bar codes and a bar-code reading device which achieves reliable reading of bar codes in a hand-held operation while maintaining a long readable range.
Accordingly, it is a general object of the present invention to provide a method of reading bar codes and a bar-code reading device which can satisfy the need described above.
Also, it is a general object of the present invention to provide a method of reading bar codes and a bar-code reading device which achieves reliable reading of bar codes in a hand-held operation while keeping a long readable range.
In order to achieve the above object according to the present invention, a method of reading a bar code based on bar-code data obtained by scanning the bar code with light and by demodulating a reflected-light signal includes the steps of a) obtaining demodulated bar-code data, b) obtaining a sum of pulse widths with respect to a predetermined number of pulses provided in at least one of a preceding portion and a following portion of the demodulated bar-code data, c) repeating the steps a) and b) once to obtain another sum, and d) making a comparison of the sum with another sum. The methods further includes a step of accepting the demodulated bar-code data as valid data when a result of the comparison satisfies a predetermined condition.
According to the method described in the above, a predetermined number of pulses provided in a portion immediately preceding the bar-code data and/or a portion immediately following the bar-code data are detected, and a sum of pulse widths of these pulses are calculated. The detection of these pulses are due to margin portions, printed patterns, characters, shadows, etc., which surround the bar code. If the bar-code reader is in motion relative to the bar-code, the pulse widths of the pulses surrounding the bar-code data should vary as the detection and demodulation of data are repeated. Because of this, a comparison of the sum obtained the first time with the sum obtained the second time makes it possible to decide whether the bar-code reader and the bar code are in relative motion.
According to one aspect of the present invention, a number as to how many pulses are in existence, rather than the sum of the pulse widths, is used for deciding whether the bar-code reader exhibits a relative motion against the bar code.
Further, the above-described method may be performed by a device for reading a bar code including a scan unit for emitting a first pattern of scan beam and a second pattern of scan beam, and a unit for using the first pattern in a first mode and using the second pattern in a second mode in order to read a bar code, the first pattern and the second pattern being selected by a user operation.
According to one aspect of the present invention, the first pattern is comprised of a plurality of scan beams, and the second pattern includes only one scan beam. That is, the first pattern is suitable for use when the bar-code reader is mounted on a counter, and the second pattern is used when the bar-code reader is pick up by the hand to read a bar-code menu or the like.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.